Science questions in on sentence. [1 M]

The outermost zone has the highest temperature in the flame. It is the hottest part of the flame. It is quite thin as compared to middle zone.

Explosive combustion is the combustion in which a substance burns suddenly and produces heat, light and sound with the help of external source of heat or pressure. E.g.:- explosion of crackers on applying heat or pressure.

Calorific Value is the term which is used to express the efficiency of a fuel.

Those substances which do not burn are called non-combustible substances. For Example- Stone, cement, glass, bricks, soil, sand, water, iron nails, copper objects.

Carbon dioxide does not support combustion and hence is considered as the best fire extinguisher for fires involving electrical equipment and inflammable materials like petrol.

Incomplete combustion of fuels produces a very poisonous gas called carbon monoxide.

In the outer zone complete combustion of the fuel takes place, so colour of the flame is blue and it is the hottest part of the flame. It is the non-luminous part of the flame.

Those substances which can burn are called combustible substances. For Example- Cloth, straw, cooking gas, kerosene oil, wood, coal, charcoal etc. A combustible substance is called as fuel.

Petrol has a lower ignition temperature. Kerosene molecules are larger than petrol molecules and hence don’t mix easily with oxygen present in air. Thus, it has higher ignition temperature than petrol.

When white phosphorus is left out open in the room temperature for some time, it burns all by itself.

Coal has the lowest calorific value. Coal contains moisture. When coal burns the moisture in coal evaporates taking away some heat of combustion which is not available for our use.

Spontaneous combustion is the combustion in which a substance burns spontaneously and produces heat and light without the help of external source of heat. E.g.:- phosphorus burns spontaneously at room temperature.

Water is conductive in nature and hence the electricity in the equipment could reach the extinguisher (the person dousing the fire using water) and can electrocute him/ her.

Charcoal does not vaporize and so does not produce a flame.

As it is a closed tank full of petrol, there will be no supply of air. Hence the petrol will not catch fire as air is necessary for the combustion of petrol.

Flame is the zone of combustion of a combustible substance. Substances which vapourise during burning produce flames. E.g.:- kerosene, wax etc.

Incomplete combustion of fuels produces a very poisonous gas called carbon monoxide.

In the middle zone partial combustion of the fuel takes place, so the colour of the flame is yellow and it is moderately hot part of the flame. It is the luminous part of the flame.

It is measured in units of energy per unit of the mass of the substance, such as: kJ/kg, J/Kg.

Charcoal does not vaporize and so does not produce a flame.

Substances which vapourise during burning, produce flames, such as wax in the candle, Kerosene. Substances which do not vapourise during burning, do not produce flames. Example- coal and charcoal.